The present invention relates to a motion control system and method for use in converting reciprocating motion of a piston to a more efficient rate of travel in proportion to crankshaft travel. This system and method are applicable to all known classic reciprocating internal combustion engines, external combustion steam engines, and can be used to integrate pneumatic and hydraulic pumps into the design.
The piston and crankshaft have been an important part of engines and pumps for scores of years. Numerous improvements have been made to the classic piston engine, including better materials, better lubricants, and improved fuel injection systems. However certain problems remain that are inherent in the classic piston engine. These problems arise because of geometrical limitations on the relationship between the piston and the crankshaft of the conventional piston engine.
In typical reciprocating engines the arcuate distance traveled by the piston rod/crankshaft connection is 1.57 times the piston stroke. Also, in classic engines, the piston travels much faster at top dead center than it does at bottom dead center due to mechanical geometric constraints. This difference in piston dwell (or rate of travel) between top dead center and bottom dead center can be as much as 60%. (Piston dwell is defined as the time taken for a fixed percentage of piston travel of total stroke.) Accordingly, piston travel is further in the first 90 degrees, as much as 15% further in the first 90 degrees than in the second 90 degrees, or the halfway point through the stroke travel.
In addition, in classic engines, the rod angularity at top dead center (angle between the major dimension of the rod and the radius of the crankshaft where the rod joins to the crankshaft at the crank arm) is 0 degrees, so in spite of high cylinder pressure, the piston cannot effectively apply useful torque into turning the crankshaft at the piston top dead center. As a result, the typical peak cylinder pressures are calibrated or timed to arrive at approximately 15 crankshaft degrees (out of 360 degrees) after top dead center so that the crankshaft and rod angularity are in position to effectively leverage the working pressure into applying torque to the crankshaft. Inevitably, this delay results in a failure to use the critical top dead center highest cylinder pressure into doing work. These higher cylinder pressures at top dead center drop precipitously as the piston travels down the bore. As the piston moves, the volume displacement increases, thus lowering the pressure at an approximate 1 to 1 ratio. For example, when the pressure is initially 500 psi at top dead center of a cylinder displacement of 30 cubic inches with a combustion chamber size of 3 cubic inches, and the piston then continues to move as little as around 15 degrees, the displacement would increase to 3.578 cubic inches, when the piston continues to move as little as 15 degrees, the piston displacement will increase to 0.578 cubic inches for an increase of approximately 20% to the combustion size, thus taking the same starting 500 psi pressure and dropping it to 304 psi. As the piston continues to move further, pressure continues to drop at a very fast rate. If the delay in peak pressure calibration timing is designed to be later in the cycle to permit the rod angularity to become more optimal for torque conversion, additional fuel energy is needed to compensate for the additional displacement beyond the 15 degrees of piston travel to maintain the same combustion PSI. In addition, this delayed gas cylinder pressure energy can vent out of the exhaust valve/port opening, lowering the expansion ratio of the combustion gases. In short, much of the potential energy is not properly utilized during the first 45 degrees of the power cycle, when the peak cylinder pressure is the highest, the result of the inherent design limitations with the classic combustion engine.
Thus there remains a need for a way to avoid these inherent design limitations of classic piston engines and pumps.